The half-life of a radioactive element is 130 days, but your sample will not be useful to you after 80% of the radioactive nuclei originally present have disintegrated. About how many days can you use the sample? Round to the nearest day.

We can use the sample about 42 days.

Step-by-step explanation:

Decay Equation:

Integrating both sides

When t=0, N= = initial amount

.......(1)

                            .........(2)

Logarithm:

130 days is the half-life of the given radioactive element.

For half life,

,   days.

we plug all values in equation (1)

We need to find the time when the sample remains 80% of its original.

We can use the sample about 42 days.

a

step-by-step explanation:

the answer is a

12

step-by-step explanation:

12 + 5 = 17

12x2=24

24-7=17